🌿 TPH in soil (C10–C40)

Environmental PN-EN ISO 16703

Overview

STATUS (as of 02.11.2026). PN-EN ISO 16703:2011 — English version (Polish title in the PKN catalogue: “Jakość gleby — Oznaczanie zawartości węglowodorów w zakresie od C10 do C40 metodą chromatografii gazowej”), published on 20.12.2011, implements EN ISO 16703:2011 and ISO 16703:2004 [IDT]; it replaced PN-ISO 16703:2009 (Polish version, withdrawn on 20.12.2011). The card has no withdrawal note — the standard is current. ISO 16703:2004 is the first edition of 1.11.2004; in the ISO catalogue it has the status “to be revised” (stage 90.92), and the draft of a new edition, prEN ISO 16703, covering C10–C40 hydrocarbons in solid matrices, has gone through the CEN public enquiry (stage 40.60, closure of enquiry) — the description follows the edition of 2004 in force.

SCOPE (clause 1). Quantitative determination of the mineral oil (hydrocarbon) content in field-moist soil samples by gas chromatography — for contents from 100 mg/kg to 10 000 mg/kg dry matter, with the possibility of adaptation to lower limits of detection. The method covers all hydrocarbons with a boiling range of 175 °C to 525 °C: n-alkanes from C10H22 to C40H82, isoalkanes, cycloalkanes, alkylbenzenes, alkylnaphthalenes and polycyclic aromatic compounds, provided they are not retained on the column during clean-up. It is not applicable to hydrocarbons below C10 originating from gasolines. From the peak pattern of the chromatogram and the boiling points of the n-alkanes (Annex B) the approximate boiling range of the oil and qualitative information on the contamination can be obtained.

WHAT THE RESULT MEASURES (3.1, clause 4). Hydrocarbon content is the sum of compounds extractable with acetone/n-heptane (2 + 1) that are not retained on Florisil and can be chromatographed on a non-polar capillary column with retention times between n-decane and n-tetracontane — mainly long-chain or branched aliphatic, alicyclic, lower polycyclic or alkyl-substituted aromatic hydrocarbons. Non-polar and weakly polar compounds (e.g. halogenated hydrocarbons) and high contents of polar compounds may interfere.

PROCEDURE (clauses 8–9). Samples are kept sealed in the dark at about 4 °C and extracted within a week, otherwise at −18 °C or lower. About 20 g of the homogenized sample is covered with (40 ± 1) ml of acetone and, after brief shaking, (20 ± 0.1) ml of the retention time window standard solution in n-heptane is added and extracted for 1 h by shaking or sonication. The organic layer is washed twice with 100 ml of water to remove the acetone (less than 0.1 % must remain in the extract), dried with sodium sulfate, and 10 ml is passed through a freshly prepared column with 2 g of Florisil and 2 g of sodium sulfate, collecting the entire eluate. The GC system must separate the n-alkanes to the baseline with a C40 response of at least 0.8 of the C20 response; three injections of the control solution — RSD at most 5 %; external calibration with at least 5 solutions of the mixture of two mineral oils with correction for column bleed; in each batch the control solution within ± 10 % of the reference value. The total area between the C10 and C40 peaks is integrated and the result in mg/kg dry matter is rounded to two significant figures. A blank higher than 10 % of the lowest value of interest requires checking of every step.

REGULATIONS. The Regulation of the Minister of the Environment of 1.09.2016 on the method of assessing land surface contamination (Dz.U. 2016 item 1395) sets no value for “C10–C40”: the risk substance is the sum of C12–C35 hydrocarbons, components of the oil fraction (aliphatic, naphthenic and aromatic, including PAHs). Permissible contents in soil according to Annex 1 as applicable from 15.05.2025 (Dz.U. 2024 item 1657): group I — 30, group II — 50, group III — 300, group IV — 3 000 mg/kg dry mass. The reference methodology is GC with FID or MS detection — a test procedure based on PN-ISO 16703 (Annex 3 point 4), i.e. the Polish version withdrawn in 2011 in favour of PN-EN ISO 16703:2011, which implements the same text of ISO 16703:2004.

WHAT WE DO NOT GIVE HERE. Example chromatographic conditions (Annex A), boiling points of the n-alkanes (Annex B), precision data (Annex C) and the recovery criterion of the Florisil check with stearyl stearate (9.5.1) — they are outside the available text of the standard.

Method principle

A known amount of the homogenized sample is extracted with acetone and n-heptane by mechanical shaking or sonication; the organic layer is separated and washed twice with water, and polar compounds are removed by adsorption on Florisil. An aliquot of the purified extract is analysed by capillary gas chromatography with flame ionization detection: the total peak area in the range delimited by n-decane and n-tetracontane is measured and quantified against an external standard — a mixture of equal amounts of two different types of mineral oil (clause 5).

Instead of n-heptane, another non-polar solvent (e.g. petroleum ether, cyclohexane, n-hexane) may be used if its suitability for the extraction of hydrocarbons from soil is proven (clause 5).

Applications

• Hydrocarbon (mineral oil) content C10–C40 in field-moist soil — from 100 to 10 000 mg/kg dry matter, with the possibility of lowering the limit of detection (clause 1)
• Approximate boiling range and qualitative information on the type of contamination from the chromatogram pattern (clause 1, Annex B)
• Assessment of land surface contamination — reference methodology for the sum of C12–C35 hydrocarbons, components of the oil fraction (Dz.U. 2016 item 1395, Annex 3 point 4)
• Outside the scope: hydrocarbons below C10 originating from gasolines (clause 1)

Key parameters

Standard

Standard number

PN-EN ISO 16703:2011

Title (PL)

Jakość gleby — Oznaczanie zawartości węglowodorów w zakresie od C10 do C40 metodą chromatografii gazowej

Title (EN)

Soil quality — Determination of content of hydrocarbon in the range C10 to C40 by gas chromatography

Step-by-step procedure

1. Sampling and storage

   Sampling according to ISO 10381-1; samples sealed, in the dark, at about 4 °C, extraction within a week — otherwise storage at −18 °C or lower; homogenization before analysis (clause 8).

2. Extraction

   About 20 g of field-moist sample or sample pretreated according to ISO 14507, (40 ± 1) ml of acetone, brief shaking by hand, (20 ± 0.1) ml of retention time window solution; extraction for 1 h by mechanical shaking or sonication; where appropriate a test portion of 5–30 g (9.3).

3. Removal of acetone

   Supernatant into a separatory funnel; wash the organic layer twice with 100 ml of water, shaking for 5 min each time, collect in a tube and dry with sodium sulfate (9.3).

4. Clean-up on Florisil

   10 ml of the extract onto a freshly prepared column with 2 g of Florisil and 2 g of sodium sulfate, without pre-washing with solvent; collect the entire eluate; PAH peaks in the chromatogram are noted in the test report (9.1, 9.3).

5. Blank

   With each batch of samples the same procedure without a sample; a value higher than 10 % of the lowest value of interest means checking every step (9.2).

6. System check and calibration

   Baseline separation of the n-alkanes, C40 response at least 0.8 of the C20 response; three injections of the control solution — RSD at most 5 %; at least 5 calibration solutions with correction for column bleed; in each batch the control solution within ± 10 % (9.4.1–9.4.4).

7. Integration and result

   Total area between the C10 and C40 peaks, with C40 integrated separately for the recovery check; content in mg/kg dry matter according to equation (1), rounded to two significant figures; peaks before C10 or a raised baseline after C40 are noted in the test report (9.4.5–9.4.7).

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• The standard gives no separate safety warning; for centrifugation it requires safety precautions, especially with regard to flammable solvents (9.3, note)

Frequently asked questions